In connection with miniaturization of semiconductor devices, microroughness of surfaces of a bare wafer and a film-coated wafer has come to have a large influence on their electrical characteristics. Since the microroughness occurs in processes such as polishing, cleaning, deposition, thermal process, and planarization, in order to make the device have high performance and improve a yield thereof, it is necessary to measure the microroughness for every process and manage a state and process conditions of a process apparatus properly.
Since an amplitude of the microroughness is very small, ranging from a subnanometer to a nanometer, its 3-D shape is measured using an atomic force microscope (AFM). However, since the measurement by the AFM requires a long time, in-line measurement of an entire surface of the wafer is substantially impossible.
On the other hand, it is known conventionally that the microroughness has correlation with light scattering. A microroughness measurement device using the light scattering method is disclosed, for example, in the U.S. Pat. No. 7,286,218 (Patent Literature 5). As other advanced technologies, Patent Literatures 1 through 4, 6, and 7 are enumerated.
Moreover, in connection with the miniaturization of the semiconductor devices, improvement of detection sensitivity for defects of a minute particle, a bump, a scratch, etc. is required over the surface of the bare wafer or the film-coated wafer.
In order to improve sensitivity of the surface inspection device using the light scattering method, it is necessary to increase a detection signal of the scattered light from a defect (a defect signal) and to reduce a detection signal of the scattered light from the microroughness (a background signal). Regarding the reduction of the background signal, filtering by signal processing is disclosed, for example, in the Japanese Unexamined Patent Application Publication No. 2007-501944 (Patent Literature 8).